package org.freertr.enc;

import java.util.ArrayList;
import java.util.List;

/**
 * ebcdic encoding
 *
 * @author matecsaba
 */
public class encEbcdic {

    /**
     * create instance
     */
    public encEbcdic() {
        if (asc2ebc != null) {
            return;
        }
        asc2ebc = reverseTable(ebc2asc);
    }

    private final static short[] ebc2asc = {
        0x00, 0x01, 0x02, 0x03, 0x9c, 0x09, 0x86, 0x7f, 0x97, 0x8d, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
        0x10, 0x11, 0x12, 0x13, 0x9d, 0x85, 0x08, 0x87, 0x18, 0x19, 0x92, 0x8f, 0x1c, 0x1d, 0x1e, 0x1f,
        0x80, 0x81, 0x82, 0x83, 0x84, 0x8e, 0x17, 0x1b, 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x05, 0x06, 0x07,
        0x90, 0x91, 0x16, 0x93, 0x94, 0x95, 0x96, 0x04, 0x98, 0x99, 0x9a, 0x9b, 0x14, 0x15, 0x9e, 0x1a,
        0x20, 0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7, 0xa8, 0x5b, 0x2e, 0x3c, 0x28, 0x2b, 0x5d,
        0x26, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf, 0xb0, 0xb1, 0x21, 0x24, 0x2a, 0x29, 0x3b, 0x5e,
        0x2d, 0x2f, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0x7c, 0x2c, 0x25, 0x5f, 0x3e, 0x3f,
        0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf, 0xc0, 0xc1, 0xc2, 0x60, 0x3a, 0x23, 0x40, 0x27, 0x3d, 0x22,
        0xc3, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9,
        0xca, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 0x70, 0x71, 0x72, 0xcb, 0xcc, 0xcd, 0xce, 0xcf, 0xd0,
        0xd1, 0x7e, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7a, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
        0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf, 0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
        0x7b, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed,
        0x7d, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, 0x50, 0x51, 0x52, 0xee, 0xef, 0xf0, 0xf1, 0xf2, 0xf3,
        0x5c, 0x9f, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5a, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9,
        0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff};

    private static short[] asc2ebc = null;

    /**
     * reverse table
     *
     * @param src source
     * @return reversed
     */
    private static short[] reverseTable(short[] src) {
        short[] res = new short[256];
        for (short i = 0; i < src.length; i++) {
            res[src[i] & 0xff] = i;
        }
        return res;
    }

    /**
     * compare tables
     *
     * @param src source
     * @param trg target
     * @return list of differences
     */
    private static List<Integer> compareTable(short[] src, short[] trg) {
        int o = src.length;
        int p = trg.length;
        if (o > p) {
            o = p;
        }
        List<Integer> res = new ArrayList<Integer>();
        for (int i = 0; i < o; i++) {
            if (src[i] != trg[i]) {
                res.add(i);
            }
        }
        return res;
    }

    /**
     * encode one byte
     *
     * @param i ascii
     * @return ebcdic
     */
    public byte encode(int i) {
        return (byte) asc2ebc[i & 0xff];
    }

    /**
     * decode one byte
     *
     * @param i ebcdic
     * @return ascii
     */
    public byte decode(int i) {
        return (byte) ebc2asc[i & 0xff];
    }

}
